async function async1() {
  console.log("async1 start"); //1
  await async2();
  console.log("async1 end"); //5 // await 语句后面的加入到微任务队列中
}
async function async2() {
  console.log("async2"); //2
}

async1();

new Promise((resolve) => {
  console.log("create micro task"); //3
  resolve();
}).then(() => {
  console.log("micro task callback"); //6
});

console.log("script start"); //4

// 输出结果:
//   async1 start
//   async2
//   create micro task
//   script start
//   async1 end
//   micro task callback
